The long term goal of the investigator is to understand the functional organization of the cell nucleus and how the processes of transcription, pre-mRNA splicing, and RNA transport are coordinated in the living cell. The short term goals are to determine the spatial organization of RNA polymerase II transcription and pre-mRNA splicing in mammalian cell nuclei. Specific studies will be aimed at determining the dynamics of splicing factors in living cells and in identifying signals involved in the movement of factors from storage and/or reassembly sites to regions of active transcription. To biochemically characterize nuclear substructures believed to be involved in splicing factor storage and/or reassembly, interchromatin granule clusters will be purified and used to obtain monoclonal antibodies. Electron microscopy in situ hybridization will be used to track the movement of several endogenous mRNAs from their sites of synthesis to the nuclear envelope. This work will serve as a framework for the examination of cells or tissues associated with various disease states with the potential for developing phenotypic screens for susceptibility and/or diagnosis of abnormalities.